Donald Trump sent out a barrage of angry tweets following the G7 summit (AP)As he flew from Canada to Singapore on Saturday night, Trump unleashed his anger on Twitter, writing: 'PM Justin Trudeau of Canada acted so meek and mild during our @G7 meetings only to give a news conference after I left saying that, "US Tariffs were kind of insulting" and he "will not be pushed around."

Based on Justin's false statements at his news conference, and the fact that Canada is charging massive Tariffs to our U.S. farmers, workers and companies, I have instructed our U.S. Reps not to endorse the Communique as we look at Tariffs on automobiles flooding the U.S. Market!

PM Justin Trudeau of Canada acted so meek and mild during our @G7 meetings only to give a news conference after I left saying that, "US Tariffs were kind of insulting" and he "will not be pushed around." Very dishonest & weak. Our Tariffs are in response to his of 270% on dairy!

Fair Trade is now to be called Fool Trade if it is not Reciprocal. According to a Canada release, they make almost 100 Billion Dollars in Trade with U.S. (guess they were bragging and got caught!). Minimum is 17B. Tax Dairy from us at 270%. Then Justin acts hurt when called out!

'Very dishonest & weak. Our Tariffs are in response to his of 270% on dairy!'

He added: 'Why should I, as President of the United States, allow countries to continue to make Massive Trade Surpluses, as they have for decades, while our Farmers, Workers & Taxpayers have such a big and unfair price to pay?

He concluded: 'Germany pays 1% (slowly) of GDP towards NATO, while we pay 4% of a MUCH larger GDP. Does anybody believe that makes sense?

'We protect Europe (which is good) at great financial loss, and then get unfairly clobbered on Trade. Change is coming!'

The attack on a long-time ally and its leader drew sharp criticism.

Why should I, as President of the United States, allow countries to continue to make Massive Trade Surpluses, as they have for decades, while our Farmers, Workers & Taxpayers have such a big and unfair price to pay? Not fair to the PEOPLE of America! $800 Billion Trade Deficit...

....And add to that the fact that the U.S. pays close to the entire cost of NATO-protecting many of these same countries that rip us off on Trade (they pay only a fraction of the cost-and laugh!). The European Union had a $151 Billion Surplus-should pay much more for Military!

....Germany pays 1% (slowly) of GDP towards NATO, while we pay 4% of a MUCH larger GDP. Does anybody believe that makes sense? We protect Europe (which is good) at great financial loss, and then get unfairly clobbered on Trade. Change is coming!

Trump trade adviser Peter Navarro said: 'There's a special place in hell for any foreign leader that engages in bad faith diplomacy with President Donald J. Trump and then tries to stab him in the back on the way out the door.'

Canada's foreign minister, Chrystia Freeland, said her country 'does not conduct its diplomacy through ad hominem attacks'.

Trudeau, who had said at the news conference that Canada would retaliate over new US tariffs, did not respond to questions about Trump when the prime minister arrived at a Quebec City hotel on Sunday for meetings with other world leaders.

The President wasted no time in making his feelings clear after the G7 summit (Rex)

Spokesman Cameron Ahmad said on Saturday night that Mr Trudeau 'said nothing he hasn't said before – both in public and in private conversations' with Trump.

Roland Paris, a former foreign policy adviser to Trudeau, took his own swipe at Trump on Twitter, writing: 'Big tough guy once he's back on his airplane. Can't do it in person... He's a pathetic little man-child.'

Trump's anger quickly turned hopeful when he later tweeted about his upcoming meeting with Kim Jong-un.

The limousine carrying the North Korean leader makes it way through the crowds in Singapore (Rex)Trump is in Singapore for a summit with Kim Jong-un (Rex)

He wrote: 'Great to be in Singapore, excitement in the air!'

Trump said he thinks 'things can work out very nicely' with North Korea on the eve of the historic summit.

He told Singapore's prime minister Lee Hsien Loong: 'We've got a very interesting meeting in particular tomorrow, and I think things can work out very nicely.'

Kim sped through the streets in a limousine after his arrival in Singapore, two large North Korean flags fluttering on the car, surrounded by other black vehicles with tinted windows and bound for the luxurious and closely guarded St Regis Hotel.

He and Trump are set to meet on Tuesday morning in the first summit of its kind between a leader of North Korea and a sitting US President.

A US official said on Monday that Trump and Kim will first meet one on one with translators in a session that could last up to two hours before they open the meeting to their respective advisers.